can someone tell me what this is.

thank you

 

junk....remove it and throw it away!!!!!

 

Its a vacuum switch, and the little doo-dad to the right of it in the clamp is a "delay valve". Both are California-model emissions pieces. I don't know if "throwing them away" is such a smart move unless your removing EVERYthing from the emissions system, like doing a header install and pulling the air pump, etc.
Stu Aull
80GS
Alaska

 

uhh the car pictured i believe has a streetport in it with full exhaust so......... in the trash it goes